We have developed a system for ultraviolet light (200 less than 2 less than 400 nm)-transformation to anchorage-independent growth of human cells in culture. We shall characterize the transformation process-wavelength dependence, influence of age and origin of cells, effect of irradiation and growth schedule, as well as the role of DNA and/or misrepair. We shall characterize the growth patterns, efficiency of anchorage-independent growth, karyotype and chromosomal banding patterns and tumorigenicity of the transformants. We shall use alkaline agarose gel techniques to detect low levels of DNA damage and repair in small quantities of non-radioactive human fibroblasts, leukocytes and skin. We shall obtain action spectra for pyrimidine dimer formation in human skin and compare it to those for ultraviolet oncogenesis in the mouse. We shall determine rates of repair of dimers by excision and by photoreactivation in human skin. We shall determine the relationship between UV transformation in vitro and solar oncogenesis in human skin, and the possible roles of DNA repair or misrepair in these processes.